1. Field of the Invention
The present invention relates to a water-based ink for inkjet recording, an ink cartridge, an ink jet recording apparatus, and an ink jet recording method.
2. Description of the Related Art
It is important for a water-based ink for inkjet recording to suppress viscosity increase and solidification due to drying in order to discharge the water-based ink stably. Thus, a humectant (antidrying agent) is generally used in the water-based ink for ink jet recording. There have been suggested, for example, a water-based ink for ink jet recording in which glycerol is used as the humectant (Japanese Patent Application laid-open No. 2011-225759) and a water-based ink for ink jet recording in which diethylene glycol is used as the humectant (Japanese Patent Application laid-open No. 2006-96990 corresponding to United States Patent Application Publication No. 2006/0146108).
However, the water-based ink for ink jet recording in which the diethylene glycol is used has the following problem. That is, although the diethylene glycol has a low viscosity, the diethylene glycol is relatively high-volatile compared with other humectants. Thus, the diethylene glycol is volatized due to drying. Therefore, the water-based ink for ink jet recording in which the diethylene glycol is used can not obtain the viscosity-increase suppressing effect after the drying sufficiently. For the water-based ink for ink jet recording in which the glycerol is used, since the volatility of glycerol is lower than that of diethylene glycol, solidification is suppressed by the glycerol even when moisture or water content is lost due to the drying. However, the viscosity of glycerol is relatively high, and thus the viscosity-increase suppressing effect after the drying is not enough. As described above, both the water-based ink for inkjet recording in which the glycerol is used and the water-based ink for ink-jet recording in which the diethylene glycol is used have the insufficient viscosity-increase suppressing effects after the drying. Thus, the water-based ink for inkjet recording in which the glycerol or the diethylene glycol is used is required to further suppress the viscosity increase after the drying. In order to stably discharge the water-based ink by suppressing the viscosity increase after the drying, it is necessary that both jetting stability after an ink jet recording apparatus is not used and is left for a short period of time (for example, a few seconds to several tens of seconds) (short-term drying) and jetting stability after the ink jet recording apparatus is not used and is left for a long period of time (for example, a month to a few months) (long-term drying) are superior. In addition, it is necessary that a re-dispersion property, which is an aspect of the jetting stability after the long-term drying, is superior.